Numerous methods and associated apparatus are well known for cleaning carpets. Several of the primary methods include: steam or hot water extraction; dry foam; and dry extraction; and rotary shampoo.
Steam or hot water extraction is currently the most popular method of cleaning. It comprises spraying hot water usually including a shampoo into the carpet and quickly extracting the solution from the carpet using vacuum. The high pressure jets of the hot water solution provide agitation of the carpet fibers while the temperature of the water, which is typically 100-180 degrees, increases the cleaning effectiveness. It is to be appreciated that for every 18 degree Fahrenheit increase in the temperature of the water, the chemical cleaning activity of the solution is doubled. Hot water extraction apparatus are available in both commercial and consumer models. Commercial models, particularly truck mounted units with heaters, high powered pumps and vacuums tend to be the most effective with consumer models that rely on hot tap water and jets of lower pressure water being somewhat less effective. Perhaps the biggest draw back to hot water extraction is that it tends to leave the carpet wet. No matter how powerful the extraction vacuum, carpets that have been cleaned using this method require 8-10 or more hours to dry. The longer period of time the carpet remains wet the greater the chance mold, mildew or other microorganisms will form in the carpet fibers.
Dry foam cleaning typically involves aerating a water solution, which contains a higher percentage of shampoo or cleaner than the hot water extraction solution, into a foam that is deposited on the carpet. Most often, the foam is worked into the carpet fibers using rotating brushes, which also agitate the carpet pile to assist in the removal of dirt. As indicated by several sources, the amount of water in the foam that comes into contact with the carpet is about 1/10 the amount of hot water extraction. Some dry foam apparatus include vacuum extractors for removing the foam while in other systems the foam residue, which encapsulates the carpet dirt, is vacuumed up after the carpet has dried. Dry foam shampoos, such as Super Carpet & Upholstery Shampoo by Franklin Cleaning Technology of Great Bend, Kans. are designed for use with cool or ambient temperature water. Advantageously, a carpet cleaned using the dry foam process dries much more quickly than a carpet cleaned by hot water extraction. While the dry foam method cleans the carpet very well, it often cannot match the cleaning effectiveness of hot water extraction due largely to the reduced chemical cleaning action of the ambient solution.
Dry extraction typically involves depositing a power (or granules) that have been pre moistened with a detergent and a dry solvent onto the carpet and working the power into the carpet fibers using mechanical brushing action. The powder picks up the dirt in the carpet. After being worked into the carpet the powder and the dirt that has attached to the powder can be vacuumed up. This process uses the least amount of water or other solvents, and accordingly, requires the least amount of drying time, if any. Unfortunately, compared with hot water extraction and dry foam, this technique does not typically remove as much soil and dirt. Because the dry extraction process is both easy and quick, it is often used between scheduled more comprehensive cleanings using other methods to help maintain high traffic areas.
The Rotary shampoo process is in many respects similar to dry foam process and often the same type of shampoo is used; however instead of aerating the shampoo to cause it to foam before applying it to the carpet, the solution is first applied to the carpet and then worked into a foam through agitation of the carpet pile by a large diameter brush of a bonnet-style carpet cleaning machine. Like the dry foam process the rotary shampoo process uses relatively small amounts of water compared to the hot water extraction process, and accordingly, dries more quickly. In one variation, the cleaning solution is sprayed onto the carpet, and in another variation, the solution is deposited onto the carpet by way of a reservoir or tank contained on the bonnet-style carpet machine. In either variation, the cleaning solution is applied to the carpet is at ambient temperature. While the aggressive agitation of the carpet pile by the brush coupled with the cleaning action of the foam provides for very good cleaning, the use of an ambient cleaning solution does not facilitate the more aggressive chemical action of the hot water extraction method.